1. Technical Field
The invention relates to an image forming apparatus, an image forming system, an image forming method, a computer-readable medium and a computer data signal.
2. Related Art
A commodity code such as EAN, JAN and UPC is used to manage commodities, and a distribution code such as ITF-14 and ITF-16 is used to manage cardboard boxes and palettes.
However, with the development of a distribution information management system such as a POS (Point Of Sale) system, an EOS (Electronic Ordering System), and an EDI (Electronic Data Interchange), more advanced commodity management, distribution management, and business management have been demanded. In order to meet such demand, the EAN international organization has developed UCC/EAN-128 as a barcode symbol for distribution compensation, which indicates distribution information or commercial transaction information. This symbol is an application standard based on CODE-128 that is a symbol standard.
Currently, the UCC/EAN-128 barcode (EAN-128: European Article Number 128 which is a barcode standardized by EAN international organization) has been used in a charge payment system of convenience stores as well as a distribution field.
The entire length of the UCC/EAN-128 is required to be less than 60 mm including quiet zones on both sides thereof, and the UCC/EAN-128 is made up of four types of line thicknesses.
Since the UCC/EAN-128 is intended to be used in a distribution field, the UCC/EAN-128 can be used to handle distribution management information and business management information.
The distribution management information specifically refers to a carton number, a shipment container code patch/lot number, date of manufacture, data of package, a warranty term, a sales term, renewal goods, a sequence number, the number of goods, a measurement unit, and the like. In addition, the business management information specifically refers to an order number, a goods consignment number, a location number (delivery point code), a cargo number, a billing source code, a purchase source code, a destination code, a returned goods management number, a service-related number, and the like.
The EAN-128 barcode includes more recorded information than a known barcode such as JAN and has a quite narrow module width. Therefore, when a barcode of EAN-128 is printed, the printing result is required to have higher precision and higher precise color. Accordingly, it is quite difficult to read the EAN-128 barcode with stable reading precision.
That is, if the EAN-128 barcode is printed with a resolution of 600 dpi, in both of white lines (hereinafter, referred to as “white bars”) and black lines (hereinafter, referred to as “black bars”), the dot configuration of the barcodes are made up of 4 dots (0.169 mm), 8 dots, 12 dots, and 16 dots, in general. Also, if the EAN-128 barcode is printed with a resolution of 1200 dpi, both of the while bars and the black bars are made up of 9 dots (0.190 mm), 18 dots, 27 dots, and 36 dots, in general. Accordingly, since the line width is considerably narrow and precise, it is difficult to print the EAN-128 barcode. If precision of the printing deteriorates, it becomes difficult to obtain stable reading precision of a barcode reader.
For example, when an electro-photographic printer (such as a laser printer) of a laser beam scanning exposure type is used, the size, shape, output and the like of a spot of a laser beam have a considerable influence on the image quality of narrow lines constituting a barcode.
With regard to horizontal lines (narrow lines perpendicular to a rotation direction of a drum or to a conveyance direction of a printing medium), a latent image is formed by scanning a surface of a charged drum-shape photoreceptor along its axial direction. Therefore, the resultant line width may become thickened due to a curvature of the drum.
Also, with regard to vertical lines (narrow lines parallel to the rotation direction of the drum or to the conveyance direction of the printing medium), the line width may become narrowed because a laser beam power sometimes become weakened when it rises.
Accordingly, a printer (image forming apparatus) for printing a barcode is desired to draw narrow lines, which constitute a barcode, so as to have an optimum width and an optimum density in order to secure stable reading.
However, the related art does not consider a printing performance (reproducibility of a line width/line density of vertical lines and horizontal lines) of an image formation means (such as a printer engine) of a printer. Accordingly, even if the amount of ejected ink or the process condition of image formation is changed, the related art may not be appropriate to print a barcode (that is, a set of narrow lines) with high precision in some cases.